Preferential multihole combustor liner

ABSTRACT

A multi-hole cooled combustor liner is provided which reduces hot streaks and associated material distress in the liner. Areas of increased cooling hole density are disposed upstream of the primary dilution holes and in circumferential alignment with fuel cup centers. Additional cooling holes are provided in between primary dilution holes are arranged in alternating pairs of circumferentially angled holes so as to provide a converging cooling air flow in the downstream direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 09/934,182, filedAug. 21, 2001, now U.S. Pat. No. 6,513,331.

BACKGROUND OF THE INVENTION

This invention relates generally to film cooled combustor liners for usein gas turbine engines and more particularly to such combustor linershaving regions with closely spaced cooling holes.

A gas turbine engine includes a compressor that provides pressurized airto a combustor wherein the air is mixed with fuel and ignited forgenerating hot combustion gases. The fuel is injected into the combustorthrough fuel tubes located at uniformly spaced injection points aroundthe combustor. These gases flow downstream to one or more turbines thatextract energy therefrom to power the compressor and provide useful worksuch as powering an aircraft in flight. Combustors used in aircraftengines typically include inner and outer combustor liners to protectthe combustor and surrounding engine components from the intense heatgenerated by the combustion process. A variety of approaches have beenproposed to cool combustor liners so as to allow the liners to withstandgreater combustion temperatures. One such approach is multi-hole filmcooling wherein a thin layer of cooling air is provided along thecombustion side of the liners by an array of very small cooling holesformed through the liners. Multi-hole film cooling reduces the overallthermal load on the liners because the mass flow through the coolingholes dilutes the hot combustion gas next to the liner surfaces, and theflow through the holes provides convective cooling of the liner walls.

In the assembled combustor, certain portions of the combustor liners arealigned with the injection points defined by the circumferentiallocation of the center of the fuel tubes. These locations arehereinafter referred to as “cup centers”. In operation, the flow ofcombustion gases past these circumferential locations create “hotstreaks” of locally increased material temperatures. The portions of thecombustor liners subject to hot streaks can exhibit oxidation, corrosionand low cycle fatigue (LCF) failures after return from field use.

Accordingly, there is a need for a combustor liner in which cooling filmeffectiveness is increased in the areas of the liner that are subject tounusually high temperatures and resulting material distress.

BRIEF SUMMARY OF THE INVENTION

The above-mentioned need is met by the present invention, which providesa gas turbine combustor liner made up of a shell having cooling holesformed therein, a group of which are disposed upstream of the dilutionholes and divided into two sub-groups. The second sub-group of thisgroup of cooling holes is located in circumferential alignment with ahot streak and are more closely spaced than the cooling holes of thefirst sub-group. The shell may also have additional cooling hole groupsdisposed between dilution holes in the liner. The additional groups arearranged so as to provide a converging flow in the circumferentialdirection to provide enhanced cooling to the area of the linerdownstream of the dilution holes.

The present invention and its advantages over the prior art will becomeapparent upon reading the following detailed description and theappended claims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter that is regarded as the invention is particularlypointed out and distinctly claimed in the concluding part of thespecification. The invention, however, may be best understood byreference to the following description taken in conjunction with theaccompanying drawing figures in which:

FIG. 1 is a cutaway perspective view of a gas turbine combustor havingcombustor liners of the present invention.

FIG. 2 is a perspective view of a portion of a combustor liner depictingangled multi-hole cooling holes.

FIG. 3 is a top view of a portion of a combustor liner depicting thearrangement of the multi-hole cooling holes of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings wherein identical reference numerals denotethe same elements throughout the various views, FIG. 1 shows a combustor10 of the type suitable for use in a gas turbine engine. Combustor 10includes an outer liner 12 and an inner liner 14 disposed between anouter combustor casing 16 and an inner combustor casing 18. Outer andinner liners 12 and 14 are radially spaced from each other to define acombustion chamber 20. Outer liner 12 and outer casing 16 form an outerpassage 22 therebetween, and inner liner 14 and inner casing 18 form aninner passage 24 therebetween. A cowl assembly 26 is mounted to theupstream ends of. outer and inner liners 12 and 14. An annular opening28 is formed in. cowl assembly 26 for the introduction of compressed airinto combustor 10. The compressed air is supplied from a compressor (notshown) in a direction generally indicated by arrow A of FIG. 1. Thecompressed air passes principally through annular opening 28 to supportcombustion and partially into outer and inner passages 22 and 24 whereit is used to cool the liners 12 and 14.

Disposed between and interconnecting the outer and inner liners 12 and14 near their upstream ends is an annular dome plate 30. A plurality ofcircumferentially spaced swirler assemblies 32 are mounted in dome plate30. Each swirler assembly 32 receives compressed air from annularopening 28 and fuel from a corresponding fuel tube 34. The fuel and airare swirled and mixed by swirler assemblies 32, and the resultingfuel/air mixture is discharged into combustion chamber 20. The combustorhas forward 60 and aft 62 ends and defines a longitudinal axis (notshown), which in the case of an annular combustor is coincident with thelongitudinal axis of the engine. It is noted that although FIG. 1illustrates one preferred embodiment of a single annular combustor, thepresent invention is equally applicable to any type of combustor,including double annular combustors, which uses multi-hole film cooling.

Outer and inner liners 12 and 14.each comprise a single wall, metalshell having a generally annular and axially extending configuration.Outer liner 12 has a hot side 36 facing the hot combustion gases incombustion chamber 20 and a cold side 38 in contact with the relativelycool air in outer passage 22. Similarly, inner liner 14 has a hot side40 facing the hot combustion gases in combustion chamber 20 and a coldside 42 in contact with the relatively cool air in inner passage 24.Both liners 12 and 14 include a large number of closely spaced coolingholes 44 formed therein.

Dilution air is primarily introduced into, combustor chamber 20 througha plurality of circumferentially spaced dilution holes 48 (FIG. 1)disposed in each of outer and inner liners 12 and 14. Dilution holes 48are generally far smaller in. number than the cooling holes 44, and eachdilution hole 48 has a cross-sectional area that is substantiallygreater than the cross-sectional area of one of the cooling holes 44.Dilution holes 48, and to a smaller extent cooling holes 44, serve toadmit dilution air into combustor chamber 20. The dilution holes arearranged in circumferentially extending bands around the periphery ofthe liners 12 and 14. The forward-most band of dilution holes 48 arereferred to as primary dilution holes.

In the assembled combustor, certain ones of the primary dilution holes48 are aligned with the injection points defined by the circumferentiallocation of the center of the fuel injectors 34 and swirlers 32. Inoperation, the flow of combustion gases past these circumferentiallocations create “hot streaks” of locally increased materialtemperatures. These streaks are not strictly longitudinal; because ofthe swirl of the flow in the combustor caused by the swirlers 32, thestreaks are curved in the circumferential direction when viewed alongthe length of the combustor. Although the prior art cooling provisionsprovide adequate cooling for the other portions of the combustor liners12 and 14, the portions of the combustor liners 12 and 14 subject to hotstreaks can exhibit oxidation, corrosion and low cycle fatigue (LCF)failures from field use.

Referring now to FIG. 2, cooling holes 44 disposed through a portion ofouter liner 12 are shown in more detail. Although FIG. 2 depicts coolingholes in outer liner 12, it should be understood that the configurationof cooling holes of inner liner 14 is substantially identical to that ofouter liner 12. As such, the following description will also apply toinner liner 14. FIG. 2 includes a frame of reference having axes labeledX, Y and Z, wherein X is the downstream axial, direction of flow(indicated by arrow B) through combustor 10, Y is the circumferentialdirection, and Z is a radial direction. Cooling holes 44 are axiallyslanted from cold side 38, to hot side 36 at a downstream angle A, whichis preferably in the range of about 15° to 20°. Cooling holes 44 arearranged in a series of circumferentially extending rows, 46. Adjacentholes 44 in each row have a circumferential hole spacing S, betweentheir respective centerlines, and adjacent rows 46 have an axial rowspacing P.

Referring now to FIG. 3, the cooling holes 44 are arranged into threeprimary groups: a group 45 located in the area aft of the primarydilution holes 48, another group 70 located in the area forward of theprimary dilution holes 48, and another group 88 disposed in the areacircumferentially in-line with primary dilution holes 48 (i.e., neitherforward nor aft of the primary dilution holes 48). The circumferentiallocation of the nearest cup center is represented by line 82 in FIG. 3.The particular primary dilution hole that is circumferentially alignedwith the cup center 82 is identified by reference number 48 a.

The group 45 of cooling holes 44 is located aft of the primary dilutionholes 48. The cooling holes 44 of this group 45 square angled downstreamin a Z direction at an angle A as discussed above. The cooling holes 44of group 45 may be all of the same diameter and cross-sectional shape inorder to ease manufacture. Alternatively, selected ones of the coolingholes 44 may have larger diameters for increased local cooling. Thecooling holes 44 of group 45 are also circumferentially slanted orclocked at a clock angle B as shown in FIG. 2. Clock angle B preferablycorresponds to the swirl of flow through combustor chamber 20, which isgenerally in the range of about 30° to 65°. In an exemplary embodiment,angle B may be about 45°.

A group 70 of cooling holes 44 is arranged around the periphery of theliner 12 upstream of the primary dilution holes 48. The cooling holes 44of this group 70 are angled downstream in a Z direction at an angle A asdiscussed above. The cooling holes 44 of group 70 may be all of the samediameter and cross-sectional shape in order to ease manufacture. Thecooling holes 44 of group 70 may be aligned parallel to the combustor'slongitudinal axis in the circumferential direction, or they may bedisposed at an angle to the longitudinal axis to better direct theairflow as desired. For example, the cooling holes 44 of group 70 may becircumferentially slanted or clocked at a clock angle B, as shown inFIG. 2 and described above. Group 70 is divided into first and secondsub-groups referenced as 71 and 72 respectively. The center-to-centerspacing of the cooling holes in the first sub-group 71 is generallyequal in the axial and circumferential directions, as described morefully below. The second sub-group 72 of the group 70 of cooling holes 44is provided to address the hot streaks in the liner 12. The coolingholes 44 of second sub-group 72 are, the same diameter as the coolingholes 44 of first sub-group 71, but they are more closely spaced inorder to provide more cooling holes 44 per unit area, as describedbelow. This denser pattern of the second sub-group 72 provides increasedcooling air flow which is used to reduce the temperature of the sectionsof the liner 12 subject to hot streaks. In an exemplary embodiment thesub-group 72 is arranged in the form of a rectangle when viewed in aradial direction.

Because of the swirl in the flow through the combustor, the hot streaksare not precisely aligned with the circumferential positions of the cupcenters 82 at the forward end 60 of the liner 12. Rather, there is someoffset of the hot streaks with respect to the cup centers 82. Therefore,the position of the sub-group 72 is selected to provide enhanced coolingin a particular circumferential location as needed. The center ofsub-group 72 may-be offset circumferentially from the cup center 82 inthe direction of the flow swirl.

Conventionally, cooling holes in typical combustor liners have verysmall diameters on the scale of about 0.02 inches (0.51 mm) andcircumferential hole spacing of about 0.13 inches (3.30 mm), or about6.5 hole diameters. The axial row spacing is generally equal to thecircumferential hole spacing. Specifically, FIG. 3 shows a portion ofcombustor liner 12 having the sub-group 71 of cooling holes 44 havingconventional spacing (i.e., circumferential hole spacing S and axial rowspacing P are both about 6.5 hole diameters or 0.13 inches (3.30 mm))and the sub-group 72 of cooling holes 44 (enclosed by dotted lines inFIG. 3) with a tighter circumferential hole spacing S′. Preferably,cooling holes 44 of sub-group 72 have a diameter of about 0.02 inches(0.51 mm) and a circumferential hole spacing S′ of about 4 holediameters or 0.08 inches (2.03 mm). It is within the scope of thepresent invention to provide the sub-group 72 with a tighter axial rowspacing; however, the axial row spacing P in sub-group 72 is preferablythe same as that of sub-group 71. By using the same hole diameter forboth sub-group 71 and sub-group 72, machining operations can beperformed continually without requiring an additional setup operation.

The cooling holes 44 of group 88 are disposed circumferentially, i.e.,same axial position, in line with primary dilution holes 48. Within thisgroup 88, sub-groups of cooling holes 44 adjacent to the primarydilution holes 48 a aligned with the cup centers 82 are disposed atalternating angles such that the holes on each side of a cup centerposition are angled towards the primary dilution hole 48 a in thecircumferential direction. In this way additional cooling flow isprovided at the circumferential location of the primary dilution hole 48a. In the exemplary embodiment shown, a first sub-group 74 of coolingholes 44 is located even with primary dilution hole 48 a in thelongitudinal direction, and is disposed to one side of the primarydilution hole 48 a in the circumferential direction. The cooling holes44 of sub-group 74 are angled in the circumferential direction so thatthey point towards primary dilution hole 48 a in the downstreamdirection. The cooling holes 44 of sub-group 74 may be angled at about+45° with respect to the longitudinal axis. Another sub-group 76 ofcooling holes 44 are located opposite sub-group 74 on the other side ofprimary dilution hole 48 a in the circumferential direction. The coolingholes 44 in sub-group 76 are angled in the circumferential directionopposite to cooling holes 44 in sub-group 74, so that this sub-group 76also directs cooling air flow to a location directly downstream ofprimary dilution hole 48 a. The cooling holes 44 in sub-group 76 may beangled at about −45° with respect to the longitudinal axis.

Additional sub-groups 78 and 80 of cooling holes 44 may be added tofurther improve cooling at the cup center position. Again referring toFIG. 3, these additional sub-groups 78 and 80 of cooling holes 44 arethe same shape and size as groups 74 and 76, and may be disposed outsideof sub-groups 74 and 76 in the circumferential direction, and may beinterspersed with additional primary dilution holes 48. In oneembodiment, groups of cooling holes 44 may be interspersed with primarydilution holes 48 in alternating order in a circumferential band aroundthe liner 12. The cooling hole sub-groups may be arranged such thatalternate pairs of hole sub-groups 74, 78 and 76, 80 are disposed atpositive and negative angles with respect to the longitudinal axis, suchthat each cup center 82 is associated with two pairs of cooling holesub-groups 74, 78 and 76, 80 arranged to converge downstream of theprimary dilution holes 48 a. In effect, the pattern of cooling holes asshown in FIG. 3, with four converging sub-groups of cooling holesarranged around primary dilution hole 48 a, would be repeated at eachcup center 82 around the circumference of the combustor liner 12.

The foregoing has described a multi-hole film cooled combustor linerhaving an improved arrangement of cooling holes to reduce temperaturegradients and hot streaks. While specific embodiments of the presentinvention have been described, it will be apparent to those skilled inthe art that various modifications thereto can be made without departingfrom the spirit and scope of the invention as defined in the appendedclaims.

What is claimed is:
 1. A gas turbine combustor liner comprising: a shellhaving forward and aft ends and defining a longitudinal axis; at leastone dilution hole formed in said shell; and a first group of coolingholes formed in said shell, said group comprising first and secondsub-groups, wherein said first sub-group of cooling holes is disposed inline with said dilution hole in a circumferential direction and on afirst circumferential side of said dilution hole, and wherein saidcooling holes of said first sub-group are angled with respect to saidlongitudinal axis in a first circumferential direction towards saiddilution hole; and wherein said second sub-group of cooling holes isdisposed in line with said dilution hole in a circumferential directionand on a second circumferential side of said dilution hole, and whereinsaid cooling holes of said second sub-group are angled with respect tosaid longitudinal axis in a second circumferential direction, oppositeto said first circumferential direction.
 2. The combustor liner of claim1 wherein said cooling holes in said first sub-group of cooling holesdefine an angle of about 45 degrees with respect to said axis, and saidcooling holes in said second sub-group of cooling holes define an angleof about −45 degrees with respect to said axis.
 3. The combustor linerof claim 2 further comprising: a third sub-group of cooling holesdisposed in line with said dilution hole in a circumferential directionand on said first circumferential side of said dilution hole; and afourth sub-group of cooling holes disposed in line with said dilutionhole in a circumferential direction and on said second circumferentialside of said dilution hole.
 4. The combustor liner of claim 3 wherein anadditional dilution hole is disposed between said first and thirdsub-groups of said cooling holes and a second additional dilution holeis disposed between said second and fourth sub-groups of said of coolingholes.
 5. The combustor liner of claim 1 further comprising at least onesecond group of cooling holes formed in said shell forward of saiddilution hole, said second group comprising first and second sub-groups,and wherein said cooling holes of said second sub-group are more closelyspaced than said cooling holes of said first sub-group.
 6. The combustorliner of claim 5 wherein the cooling holes of said second group areparallel to said axis in the circumferential direction.
 7. The combustorliner of claim 5 wherein the cooling holes of said second sub-group ofsaid second group are disposed in a generally rectangular pattern, thecenter of said pattern being offset in a circumferential direction fromthe center of said dilution hole.
 8. The combustor liner of claim 7wherein said shell has an annular configuration and said cooling holesof said first and second sub-groups of said second group of coolingholes are all arranged in a series of circumferentially extending rows,wherein adjacent cooling holes in each row have a circumferential holespacing and adjacent rows have an axial row spacing.
 9. The combustorliner of claim 8 wherein the circumferential hole spacing of said secondsub-group of said second group of cooling holes is less than thecircumferential hole spacing of said first sub-group.
 10. The combustorliner of claim 9 wherein the circumferential hole spacing of said firstsub-group of said second group of cooling holes is equal to about 6.5hole diameters.
 11. The combustor liner of claim 10 wherein thecircumferential hole spacing of said second sub-group of said secondgroup of cooling holes is equal to about 5 hole diameters.